Name:	cmre_CarryingCapacityOfVesselsAtPeriodEndTEU
Namespace Prefix:	cmre_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Amount agreed to invest.

No definition available.

Name:	cmre_InvestmentAgreedAmount
Namespace Prefix:	cmre_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The number of container vessels.

No definition available.

Name:	cmre_NumberOfContainerVessels
Namespace Prefix:	cmre_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Information pertaining to the number of controlled entities.

No definition available.

Name:	cmre_NumberOfControlledCompanies
Namespace Prefix:	cmre_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

The number of controlled companies that currently own dry bulk vessels.

No definition available.

Name:	cmre_NumberOfControlledCompaniesDryBulkVesselsOwned
Namespace Prefix:	cmre_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

The number of controlled companies that have previously owned and sold or have agreed to sell their dry bulk vessels.

No definition available.

Name:	cmre_NumberOfControlledCompaniesDryBulkVesselsPreviouslyOwnedOrTobesold
Namespace Prefix:	cmre_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

The number of controlled companies which will be used for future dry bulk vessel acquisitions.

No definition available.

Name:	cmre_NumberOfControlledCompaniesDryBulkVesselsTobeacquired
Namespace Prefix:	cmre_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

The number of majority owned subsidiaries.

No definition available.

Name:	cmre_NumberOfMajorityOwnedSubsidiaries
Namespace Prefix:	cmre_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

The number of subsidiaries owned by the entity.

No definition available.

Name:	cmre_NumberOfSubsidiaries
Namespace Prefix:	cmre_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

This item represents the percentage of ownership of a related party.

No definition available.

Name:	cmre_PercentageOwnership
Namespace Prefix:	cmre_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

Amount of net assets (liabilities).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 205
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479938/205-30-45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 205
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479910/205-30-50-1

Name:	us-gaap_AssetsNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Percentage of voting equity interest acquired in business combination.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 805
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479328/805-10-50-8

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 805
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 38
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479303/805-10-55-38

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479328/805-10-50-2

Name:	us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

Name:	us-gaap_CommonStockSharesOutstanding
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

The number of new shares issued in the conversion of stock in a noncash (or part noncash) transaction. Noncash is defined as transactions during a period that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482913/230-10-50-3

Name:	us-gaap_ConversionOfStockSharesIssued1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

Amount of cash outflow for cost from early extinguishment and prepayment of debt. Includes, but is not limited to, third-party cost, premium paid, and other fee paid to lender directly for debt extinguishment or debt prepayment. Excludes accrued interest.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 15
-Subparagraph (g)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-15

Name:	us-gaap_PaymentsOfDebtExtinguishmentCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The distributions of earnings to an entity that is affiliated with the reporting entity by means of direct or indirect ownership.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 15
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-15

Name:	us-gaap_PaymentsOfDistributionsToAffiliates
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Number of shares issued during the period from a dividend reinvestment plan (DRIP). A dividend reinvestment plan allows the shareholders to reinvest dividends paid to them by the entity on new issues of stock by the entity.

Name:	us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

Number of new stock issued during the period.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480008/505-10-S99-1

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480070/505-10-S50-1

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S45
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480100/505-10-S45-3

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480100/505-10-S45-2

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477657/942-210-S45-1

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478478/942-210-S50-1

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(20))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(19))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 11
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480657/210-10-S50-11

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478448/946-505-50-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-09(4)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-3

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-03(i)(1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479886/946-10-S99-3

Name:	us-gaap_StockIssuedDuringPeriodSharesNewIssues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

Name:	srt_StatementGeographicalAxis=country_LR
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_StatementGeographicalAxis=country_MH
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	dei_LegalEntityAxis=cmre_CompanyIncorporatedUnderLawsOfJerseyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_StatementGeographicalAxis=country_JE
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_CommonStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_BusinessAcquisitionAxis=cmre_NeptuneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_PreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_CounterpartyNameAxis=cmre_NeptuneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_CounterpartyNameAxis=cmre_CostamareBulkersHoldingsLimitedCbhlMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_CounterpartyNameAxis=cmre_CostamareBulkersIncCbiMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_CounterpartyNameAxis=cmre_CostamareShareholdersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	dei_LegalEntityAxis=cmre_CostamareBulkersIncCbiMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_OwnershipAxis=cmre_KonstantakopoulosFamilyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: